Reductio ad Absurdum

reductio ad absurdum

(also known as: reduce to absurdity)

Description: A mode of argumentation or a form of argument in which a proposition is disproven by following its implications logically to an absurd conclusion. Arguments that use universals such as, “always”, “never”, “everyone”, “nobody”, etc., are prone to being reduced to absurd conclusions. The fallacy is in the argument that could be reduced to absurdity -- so in essence, reductio ad absurdum is a technique to expose the fallacy.

Logical Form:

Assume P is true.

From this assumption, deduce that Q is true.

Also, deduce that Q is false.

Thus, P implies both Q and not Q (a contradiction, which is necessarily false).

Therefore, P itself must be false.

Example #1:

I am going into surgery tomorrow so please pray for me. If enough people pray for me, God will protect me from harm and see to it that I have a successful surgery and speedy recovery.

Explanation: We first assume the premise is true: if “enough” people prayed to God for the patient's successful surgery and speedy recovery, then God would make it so. From this, we can deduce that God responds to popular opinion. However, if God simply granted prayers based on popularity contests, that would be both unjust and absurd. Since God cannot be unjust, then he cannot both respond to popularity and not respond to popularity, the claim is absurd, and thus false.

Example #2:

If everyone lived his or her life exactly like Jesus lived his life, the world would be a beautiful place!

Explanation: We first assume the premise is true: if everyone lived his or her life exactly like Jesus lived his, the world would be a beautiful place. If this were true, we would have 7 billion people on this earth roaming from town to town, living off the charity of others, preaching about God (with nobody listening). Without anyone creating wealth, there would be nobody to get charity from -- there would just be 7 billion people all trying to tell each other about God. After a few weeks, everyone would eventually starve and die. This world might be a beautiful place for the vultures and maggots feeding on all the Jesus wannabes, but far from a beautiful world from a human perspective. Since the world cannot be both a beautiful place and a horrible place, the proposition is false.

The only problem with the second example is that no money doesn't lead to death if every producer is willing to feed those non producers. If everyone lived like Jesus then there would not be any wealth is true. However this would then conclude that people would just live without wealth. The failure of Marxism wasn't due to people helping each other was wrong it was because people can be forced into altruism. Thus if everyone suddenly followed what Jesus would do, there would be no failure because by assumption no one would not follow altruistic behavior :) (btw the Gospels don;t say Jesus hates wealth it just says that he hates hoarding when the hoarders don't help those that need it)

@Bo Bennett, PhD: thats an overly literal fallacy beacuse no one means do the exact job of individual x when your suppose to be like x, it just mean to emulate their character traits. No christian has ever said it should be illegal to be a non-carpenter which is also a straw man. Its also absurd to think when Johnny said that I want to be like their dad one day, that Johnny meant he wanted to marry his mother.

@Bo Bennett, PhD: Given your particular version of that argument however its perfectly fine to say its absurd to take it literal, however hopefully my other comment shows its absurd to take anyone literal in that context. :P

@:P: This is a website about fallacies. Errors in reasoning. In order to demonstrate these fallacies I give examples. Some examples are common that one might see often, others are more exaggerated and quite rare in order to make the fallacy more clear. Every example is fallacious. If you say "nobody would say that," you might be right - but I am not claiming they would (strawman). Readers get emotional over the examples because they feel they make them look bad through association. I have taken heat from Christians, creationists, flat-earthers (they are the most nasty), atheists, liberals, conservatives, and even ghost hunters. My message to everyone - stop taking these examples personally unless you look at the example fallacy and say "that makes perfect sense to me... I see nothing wrong with that." Otherwise, we are in agreement.

I also wondered about this example. I think the fallacy (not a logical fallacy I suppose) is of taking the proposition too literally. If you wanted, you could argue that living one's life "exactly like Jesus lived" would involve living in the area of 1st-Century Israel, performing miracles, being crucified and rising from the dead, etc. But clearly the loosely-worded proposition doesn't mean that.Given that, why should one think it means "roaming from town to town, living off the charity of others, [and] preaching about God" rather than something more like :P's suggestion of emulating his character traits?So yes, you can use reductio ad absurdum to show that the proposition, if taken literally, is false, but if it wasn't meant to be taken that literally, is this response then effectively a strawman fallacy?

@Philip J. Rayment: If the arguer in the example mean simply emulating character traits, then yes, the response would be a strawman. Someone has said this to me before (this is where the example comes from). I did ask for clarification because I did not understand what they meant. The conversation went on for about an hour. At the start, they meant much more than "emulating character traits" and I used this technique until we agreed that it would be great for people to be kind to each other. For example, the person claimed that one should devote their life to God rather than have a family. I pointed out that this would lead to the end of humanity in one generation if everyone did this. My example is a short and sweet example of the Reductio ad Absurdum.

This is a blatantly biased website against Christians. A general example would be much more appropriate. People come onto these websites to learn about argument, not to have a God bashing session.Prayer is a general appeal to God, much like a letter to a Senator, which can be rejected or accepted. God will do what he sees fit. If your prayer fits in to His schedule, it will be done. Otherwise, God will carry out His will, not yours.The obvious intention of the second example is to state that we should follow the principles demonstrated by Jesus's life, not that we should literally act exactly as he does. Love God with all your heart, mind, and soul. Love your neighbor as yourself. If everyone followed these principles, the world would be a better place. Of course, you can not love anyone if you are starved to death and expect others to provide the funds for your gifts to no one. Jesus would not preach to believers something they already know, he would only strengthen it. Nor would Jesus starve himself to death. Your assumptions are unrealistic. However, if everyone worshiped God, worked hard to improve their lives, and helped to improve other people's lives, the world would be perfect.All your conclusions based on the proposed statement are valid, but the wording of the examples are obviously biased to lead your reader to believe that Christian arguments are generally invalid.

If you make it past one example that offends you, you will find that I am an equal opportunity "basher," where I highlight bad arguments from Christians, Muslims, Atheists, Liberals, Conservatives, men, women, etc. My examples are of bad (fallacious) arguments—I don't care who makes them. You are committing a strawman in your defense of "living like Jesus." The argument is "If everyone lived his or her life exactly like Jesus lived his life," you are talking about "loving God and neighbors." By talking out the absurd conclusions of this scenario, we might ultimately get to the arguer rewording his argument to something such as "I meant if everyone follows Jesus' advice of loving God and loving your neighbor," then the argument would have advanced. This is the entire point of this strategy. If you want to avoid fallacies, shelve your emotion and defensiveness and approach the argument objectively.

Who told you that? And what made you decide to believe it? These aren't rhetorical questions.

"God will do what he sees fit" isn't a factual statement. It's a belief. Forget whether it's a good or bad belief, I personally think it's fine as beliefs go. But this is a logical fallacy site. It's just important to realize that what you're saying is a belief. Not a factual statement.

I have to agree with Electro_blob that this website is blatantly biased against Christians. In order to base this on more than just the examples on this page, I did a bit of research. I couldn't find a "random fallacy" button, so I opted for doing a search on a couple of key words, 'evolution' and 'Bible'. I checked every hit, and only discarded ones where the hit was on a word containing the search term (i.e. revolution) or was simply in a reference or something.

I looked to see whether the example fallacy was presented as from a "Christian" (including creationist, IDer, or anti-evolutionist) or presented as from a "non-Christian" (including evolutionist, anti-creationist, or anti-IDer).These are my results for "evolution"

Strawman—Christian (x 2)

Confusing an Explanation with an Excuse—unclear

Definist Fallacy—Christian (x 1), non-Christian (x1)

Extended Analogy—Christian

Appeal to Complexity—Christian

Appeal to Definition—Christian (not in the main example, but in the 'exception' example)

Appeal to Ridicule—Christian (x 1), non-Christian (x 1)

Pseudo-Logical-Fallacies—Christian (not an example, because not a fallacy, but making out that the "Christian" view is wrong.

Appeal to Authority—Non-Christian, although the explanation is against the "Christian" view.

This leaves a total of 24 cases where the fallacy is in the mouth of a Christian (or similar), and four cases where the fallacy is in the mouth of a non-Christian (or similar). (And that doesn't include this page, because it doesn't have either of those search terms.)

So your claim that you "highlight bad arguments from Christians, Muslims, Atheists..." is correct, but your preceding claim that you are "an equal opportunity "basher," " seems to be incorrect.I grant that despite my attempts at objectiveness, my choices of search words might have slanted the results, but prima facie, based on the examples, there does seem to be a strong anti-Christian bias on this site.

Electro_blob referred to the "second example", and you replied regarding the examples, so I concentrated on examples of fallacies, but adding in assertions you've made in explanations, comments, etc., makes it quite clear that this site does take an anti-Christian stance. Which is not surprising from an atheist, but it should be acknowledged, not denied.

@Philip J. Rayment: You might be conflating anti-science with Christianity. I am fervently against anti-science. I say so in the introduction that many examples are from Creationists, which is a minority subsection of Christians.

Even discounting the creationist ones, there are significantly more cases of putting the fallacy in the mouth of a Christian than a non-Christian, so no, that doesn't explain it.

conflating anti-science with Christianity. ... I say so in the introduction that many examples are from Creationists...

Talk about conflating! Creationists are most definitely NOT anti-science. It was largely creationists who founded modern science, many creationists are practising or former scientists, and creationists use (among other things) arguments from science, including (accurately) quoting evolutionists. To describe them as anti-science is simply a baseless slur and not becoming someone who (presumably) thinks themselves rational.

...Creationists, which is a minority subsection of Christians.

And yet, Christians supposedly get their beliefs from the Bible, which clearly and unambiguously teaches a creationist point of view.

"This is a blatantly biased website against Christians" Ad Misericordiam Fallacy. A fallacy of distraction that attempts to distract from the truth or validity of an argument by appealing to pity.

I suppose if we follow your wounded reckoning a website devoted to auto mechanics could be accused of being "biased" against "Foodies". Most of the logicians, newbies and seasoned vets I read and respect in these threads could give a fig about a participant's religious affiliation. To begin an argument by announcing oneself a Christian is an irrelevant thesis and commits the logical fallacy of "special pleading".

What are you implying by calling oneself a Christian? Do the Laws of Physics not apply to you? Do you regard faith to be greater than evidence? Are you capable of logical ratiocination? Do you maintain that theology is a superior epistemology to the Socratic method or scientific methodology? Are you yourself so biased by your beliefs that your entire frame of reference, apologetics, revisionist history and awe of the supernatural supersedes other cognitive disciplines?

Curiously none of these predicates are made, assumed or assigned by the logicians here by whim or bias, and yet they are almost always the first claim announced by Christians entering the forum. If not by appellation than either by poisoning the well or accusing others of being anti-Christian, atheists or non-believers. As a rule of thumb, most of us are unimpressed by the special pleading of Christianity, or the ad hominem label of atheist. These labels offer no special advantage to an argument. For one, the claim is too broad and subjective to even verify. (See Dr. Bo's Amazing Familiarity fallacy). Even Christians can't make up their minds about who and who isn't a bonafide Christian. So the argument is moot from the start. The same can be said of any religious or non-religious affiliation. Under the rules of logical debate (Aristotle's Analytics), one is under no obligation to pursue an irrelevant thesis or petitio principii (loaded, begged Question). One's belief claims are irrelevant to the specific argument. We argue the logic and dismiss the detritus.

Another recurring error is when one starts a claim by saying, "I believe". This is a site for logical fallacies and not personal belief. If you start an argument with I Believe your argument can be readily dismissed without further adieu. Now you can say we are biased against believers, but the truth is we do not debate beliefs here only the flaws and errors in reasoning that lead to paralogical or misological conclusions.

As Carl Sagan famously said, "Extraordinary claims require extraordinary evidence", or as Christopher Hitchens restated, "What can be asserted without evidence can be dismissed without evidence". Most Logicians dismiss the claim of Christianity offhand not from prejudice, but because belief, faith, and doctrine typically predicate the argument or claim in question. So the bias here is not against Christians, per se, but fallacious reasoning as an error in cognitive construction.

@Michael Chase Walker: Oh my, what a breath of fresh air. These are the words I've been searching for on this forum since joining and seeing the ridiculous upset over religion. Thank you for taking the time to clearly lay out the logical concepts regarding what really should not be an issue in a forum like this in the first place, and that's people's cosmological beliefs.

It makes no sense to try and apply logic to ones personal religion, whatever flavor. To repeat from above: "one's belief claims are irrelevant to [any] specific argument." This is a place to educate and clarify logic and learn how to recognize and dismiss fallacies. Taking offense because of ones Christian or Muslim beliefs is just silly, and so not the point. Beliefs don't have logical stand to them, but that doesn't mean you have to stop believing them.

First time I ever got so much more bang than buck when searching a simple definition. I commend the material, and I commend the writer for adding so much more to it through their beautifully wrought examples. I am pure entertained.

Ok. Very enlightening. But you should have added another fallacy: The Straw Man Fallacy. Anyone desiring two good examples need look no further than those given above about prayer and Christ-likeness. A more impressive use of your time would be seeing how many Christians you could find who would actually explain their understanding of prayer or Christ-likeness in the terms given above. I'll save you some time: You would find none. A child of 8 raised in a mature Christian home could easily distinguish between the nonsense above and the actual beliefs of Christianity. No, 6. No, 5. Maybe younger. But friend, I sympathize with you. I am well acquainted with the miserable task of the anti-Christian who makes the mistake of taking on an educated Christian in debate. Much, much safer to offer the most childish interpretation of Christianity imaginable and then attack that. You would have no hope against the Real Thing.

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